In the 2016 Base QRDA-1 HL7 IG (i.e. "HL7 CDA® R2 Implementation Guide: Quality Reporting Document Architecture Category I (QRDA I); Release 1, DSTU Release 3 - US Realm, Draft Standard for Trial Use, Volume 2 - Templates and Supporting Material, June 2015") there is this constraint:

7. SHALL contain exactly one [1..1] effectiveTime (CONF:1098-7508) such that it
Note: This effectiveTime represents either the medication duration (i.e., the time the medication was started and stopped) or the single-administration timestamp.
a. SHOULD contain zero or one [0..1] @value (CONF:1098-32775).
Note: indicates a single-administration timestamp
b. SHOULD contain zero or one [0..1] low (CONF:1098-32776).
Note: indicates when medication started
c. MAY contain zero or one [0..1] high (CONF:1098-32777).
Note: indicates when medication stopped
d. This effectiveTime SHALL contain either a low or a @value but not both (CONF:1098-32890).

This is a horribly written constraint. As a 'such that' clause, the initial constraint should be followed by a list of 'SHALL' statements that define the list of characteristics the author says are required to meet the initial constraint.

It makes no sense to follow the initial 'such that' constraint with anything other than 'SHALLs' but this constraint has two meaningless SHOULDs and also a MAY.

In an attempt to make sense of this, the ESAC developers ignored the 'such that' clause and implemented this as 5 separate assertions.

Unfortunately, even as separate constraints they contradict each other. They say you SHOULD have a 'low' element and you SHOULD have an @value attribute but then there is a SHALL that says you must have one or the other but not both.

What this means is that no matter how you enter this time you will get either a warning message or and error message. There is no way to provide this time without the system telling you that you've done something wrong.